Field of the Invention
The invention relates to a method for synchronizing at least two control devices.
Modern motor vehicles are frequently equipped with a multiplicity of control devices. In each case one or more control devices are provided for controlling engine operating functions, and if appropriate, for actuating throttle valves, electromechanical actuator drives or a crankshaft starter generator (KSG), or further actuators.
Various actuator elements, for example injection valves, spark plugs and charge cycle valves, are actuated by the control device or devices as a function of the angular position of the crankshaft of the internal combustion engine.
For this reason, in internal combustion engines, a sensor device is provided which has an incremental angle encoder and a measuring sensor which generates a measuring signal. The measuring signal is preferably a pulse sequence.
The individual control devices are connected to the sensor device via a signal line and receive the measuring signal. They process the measuring signal further by counting the pulses.
The counter readings or angular values of the conditioned measuring signals derived therefrom can be distinguished in the individual control devices as a function of when the respective control device starts counting the pulses and as a function of instances when individual pulses are registered incorrectly or else instances in which they are not registered.
In order to exchange information, individual control devices are connected via a data bus, for example the CAN (Controller Area Network) bus. For example, control instructions for actuating charge cycle valves are transmitted at predefined angles of the crankshaft by the control device for controlling engine operating functions. Reliable operation of the motor vehicle in which the control devices are arranged can be ensured only if the conditioned measuring signals are synchronized in the individual control devices.
Issued German Patent DE 41 40 017 C2 discloses a method for operating computer units that communicate with one another via a data bus by exchanging data serially. Each of the computer units has its own timer system. A time registration signal is fed into the data bus once or repeatedly. Each computer unit stores its own time value when the time registration start signal is identified. One of the computer units then transmits its own stored time value to the other computer units. The other computer units synchronize their own time base as a function of their own stored time value and the time value of the other computer unit. There is no central clock supply provided for the computer units.
It is accordingly an object of the invention to provide a method for synchronizing at least two control devices that is reliable and simple.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for synchronizing at least a first control device and a second control device. The method includes steps of: providing a communication link between the first control device and the second control device; providing a sensor device having a measuring sensor for generating a measuring signal and a device selected from the group consisting of an incremental angle encoder and a position encoder; assigning a synchronization device to the first control device and to the second control device, and configuring the synchronization device for generating a synchronization signal; generating a conditioned first measuring signal in the first control device as a function of the measuring signal; generating a conditioned second measuring signal in the second control device as a function of the measuring signal; in the first control device, receiving the synchronization signal at an instant of time and obtaining a value of the conditioned first measuring signal at a predefined time after the instant of time that the synchronization signal was received by the first control device; in the second control device, receiving the synchronization signal at an instant of time and obtaining a value of the conditioned second measuring signal at a predefined time after the instant of time that the synchronization signal was received in the second control device; transmitting the value of the conditioned first measuring signal obtained at the predefined time after the instant of time that the synchronization signal was received by the first control device, from the first control device to the second control device; with the second control device, synchronizing the conditioned second measuring signal dependent upon a difference value; and obtaining the difference value by taking a difference between the value of the conditioned first measuring signal obtained at the predefined time after the instant of time that the synchronization signal was received by the first control device and the value of the conditioned second measuring signal obtained at the predefined time after the instant of time that the synchronization signal was received by the second control device.
In accordance with an added feature of the invention, the conditioned first measuring signal is generated by counting edges of the measuring signal; and the conditioned second measuring signal is generated by counting edges of the measuring signal.
In accordance with an additional feature of the invention, the synchronization device is configured as part of the sensor device.
In accordance with another feature of the invention, before transmitting the value of the conditioned first measuring signal from the first control device to the second control device, the value of the conditioned first measuring signal is set to a setpoint value.
With the foregoing and other objects in view there is also provided, in accordance with the invention, a method for synchronizing at least a first control device and a second control device in which the method includes steps of: providing a communication link between the first control device and the second control device; providing a sensor device having a measuring sensor for generating a measuring signal and a device selected from the group consisting of an incremental angle encoder and a position encoder; assigning a synchronization device to the first control device and to the second control device, and configuring the synchronization device for generating a synchronization signal; generating a conditioned first measuring signal in the first control device as a function of the measuring signal; generating a conditioned second measuring signal in the second control device as a function of the measuring signal; in the first control device, receiving the synchronization signal at an instant of time and setting a value to a setpoint value, the value being a value of the conditioned first measuring signal at a predefined time after the instant of time that the. synchronization signal was received by the first control device; in the second control device, receiving the synchronization signal at an instant of time and obtaining a value of the conditioned second measuring signal at a predefined time after the instant of time that the synchronization signal was received in the second control device; transmitting the value of the conditioned first measuring signal at the predefined time after the instant of time that the synchronization signal was received by the first control device, from the first control device to the second control device; with the second control device, synchronizing the conditioned second measuring signal dependent upon a difference value; and obtaining the difference value by taking a difference between the value of the conditioned first measuring signal at the predefined time after the instant of time that the synchronization signal was received by the first control device and the value of the conditioned second measuring signal obtained at the predefined time after the instant of time that the synchronization signal was received by the second control device.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method for synchronizing at least two control devices, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.